Background & Aims: Due to the adverse effects of synthetic antioxidants, there is a great desire to use herbs because of its antioxidant properties. This study was performed to examine the antioxidant effects of (Pimpinella affinis) as an alternative to synthetic antioxidants.Materials & Methods: Total phenolic, contents were measured with folin ciocalteu method. The antioxidant capacity of the extract and essential oil was assessed by DPPH (2,2-diphenyl-1- picrylhydrazyl) radical-scavenging activity and compared to synthetic antioxidant BHT. In addition, antioxidant capacity of extracts was also analyzed with ABTS (acid sulphonic-6-ethylbenzthiazoline-3-azinobis, 2, 2, cation radical method. Data were analyzed using Duncan's multiple tests and the analysis was carried out using SPSS.Results: In testing percent of inhibition of free radicals (DPPH), the extract showed a significant inhibitory effect compared to the essential oil (p<0.05). Both extract and essential oil also showed iron reducing effect that was affected by the increase in the concentration. In ABTS test, most antiradical activity related to the concentration of 4 mg/ml with 24% and 92% inhibition, respectively when compared with BHT showed less inhibitory effect. And finally total phenolic content of essential oil and extract was 53.14±4.25 and 37.68±1.12 mg Gallic acid/g extract, respectively.Conclusion: The results of this study showed that extract and essential oil of Pimpinella affinis have considerable antioxidant activity compared to synthetic antioxidant (BHT), and after conducting more comprehensive studies can be used in food and pharmaceutical industries.